Adaptive Stiffness and Damping Shock Absorption Mechanisms and Control Strategies for General Aviation Aircraft Landing Gear: A Systematic Review with Future Roadmap

General aviation has experienced sustained global growth, yet landing safety attracts significant attention, with nearly 60% of accidents occurring during ground operations and take-off or landing phases. The expanding operational scenarios of general aviation towards unpaved and non-standard airfields have led to an increasing demand for high-performance landing gear shock absorption systems. Mechanical variable stiffness and damping serves as a conventional and mature solution, but it cannot maintain optimal performance across the full range of varying landing and taxiing conditions. Adaptive stiffness and damping technologies offer a promising R&D direction to overcome the limitations of traditional landing gear designs. However, no previous review has examined both their mechanisms and control strategies together from the general aviation perspective. This review follows the PRISMA methodology to propose a hierarchical assessment framework for variable stiffness and damping mechanisms in general aviation landing gear, covering the representative spectrum from conventional passive mechanisms to adaptive solutions. The potentially transferable concepts from other aircraft categories and non-aviation domains are also identified to strengthen and broaden the technical pathways, and their suitability for general aviation aircraft is critically assessed. Adaptive control strategies addressing three categories of external uncertainties are reviewed and compared, namely uncertain sink speed and landing weight, uncertain landing attitude, and uneven operating surfaces. Technology readiness, airworthiness requirements, and practical implementation concerns are systematically discussed, revealing notable challenges in transitioning from laboratory research to engineering applications. Finally, a three-term roadmap is proposed to outline the future research priorities, including hardware maturity enhancement, networked cooperative control, and AI-enabled autonomous adaptation. The findings presented herein provide an integrated reference for researchers and industry practitioners and are intended to foster the advancement of adaptive shock absorption systems for general aviation aircraft landing gear.